Using the principles of operant conditioning, factors will be studied which influence the maintenance of ethanol self-administration by rats and Rhesus monkeys. Ethanol serves as a reinforcer for those behaviors which lead to its presentation. Thus, methods used in analyzing other reinforcers may be applied to ethanol. Variables affecting ethanol self-administration can be divided into past history factors (e.g., prior drug experience), current circumstances (e.g., food deprivation), and response consequences (e.g., ethanol concentration). These variables will be studied parametrically, i.e., across a range of values, and interactions between variables will be systematically explored. The objectives of this research are: (1) to investigate functional relations between factors thought to effect ethanol self- administration and the several measures related to ethanol intake and its behavioral effects, (2) to study the interaction between variables thought to influence ethanol dependence, and (3) to assess the relative importance of the variables studied. These objectives will have two consequences. One will be results which can resolve conflicts between published studies that used only a single parametric value for each independent variable (e.g., one ethanol concentration). A second consequence will be systematized knowledge upon which an analysis of the complicated phenomena of human ethanol dependence can be made.